[IMP] website: allow to have custom slug

Now, slug uses seo_name if field exists before to fallback on display_name.

It allow to have a custom url without change the product name already used in
backend e.g. or just because you want add some keywords for seo.

task-2291676

addons/http_routing/models/ir_http.py

@@ -92,7 +92,7 @@ def slug(value):
         if not value.id:
             raise ValueError("Cannot slug non-existent record %s" % value)
         # [(id, name)] = value.name_get()
-        identifier, name = value.id, value.display_name
+        identifier, name = value.id, getattr(value, 'seo_name', False) or value.display_name
     else:
         # assume name_search result tuple
         identifier, name = value

addons/website/models/mixins.py

@@ -23,6 +23,7 @@ class SeoMetadata(models.AbstractModel):
     website_meta_description = fields.Text("Website meta description", translate=True)
     website_meta_keywords = fields.Char("Website meta keywords", translate=True)
     website_meta_og_img = fields.Char("Website opengraph image")
+    seo_name = fields.Char("Seo name", translate=True)
 
     def _compute_is_seo_optimized(self):
         for record in self: